A line telephone stations, often referred to as "trader turrets", are widely used in financial trading networks such as between banks, brokerage houses, and other types of financial institutions. Telephones of this type provide access to a large number of telephone lines, typically a hundred or more. A line is selected by depressing a single key. A trading room can include many telephone key stations so that many transactions can be completed simultaneously.
Each key telephone station in a trading room has voice channel access to other stations in the trading room and to a large number of outside lines of different types (public, private, four wire etc.) Normally each outside line is available at several stations so that any one of several traders can pickup an incoming call. A status indication is provided for each voice channel at each station where the line is available to indicate ringing, busy, hold, idle, conference, etc. The status line indications are supplied through a separate data channel for all the lines available at a station. This status information is invaluable to the operator since it provides an overall picture of the trading activity. A major obstacle to providing remote turret interconnections to a trading room, however, is the difficulty in providing the necessary data channel information of line status to the remote location.